My 440 EX is having issues running. When riding at higher throttle it revs out then boggs out like its running out of fuel. It sat for a 6-8 months before this started happening. Could the petcock be clogged up or should I look somewhere else????

 

My 450 just took a month month rest, after knee surgery. It would not run right, after new fuel, new spark plug and gleaning the pilot and mainjet. I took the air screw out and it had black goo on the tip. I cleaned that off and now it runs the way it should.